The present invention is directed to an electromagnetic relay, and more particularly to the construction of an electromagnetic relay of the type having at least one double-throw switch in which a pair of movable contacts are biased toward a fixed common contact and are driven in the direction of being released from the fixed common contact against the biasing forces thereof for closing and opening contact operations.
The relays of the above switch arrangement are frequently referred to as card relays of lift-off type in contrast to the conventional relays of so-called flexure type which has the same double-throw switch arrangement but has a different contact arrangement of forcibly moving or flexing a common contact disposed between a pair of fixed contacts and normally retained in spaced relation thereto into the contacting engagement therewith at the time of closing operation. Such relays of flexure type have been widely used to an extent that they may be regarded as a standard type relay in certain application field. In recent years, however, the above card relays of lift-off type have an increased chance to be utilized in place of the flexure-type relays of the like operating performance or like dimensions. The problem occurs when substituting the card relays of lift-off type for the relays of flexure type since they have different terminal arrangements and require different wiring or sockets, rendering such substitution very complicated and cumbersome. That is, as exemplarily shown in FIG. 1, the flexure relay 1 of general-purpose type has a universal terminal arrangement in which normally closed (NC) terminal lugs 2A, normally open (NO) terminal lugs 3A, and common (COM) terminal lugs 4A are disposed in this order due to its structural requirement of supporting common contacts 4 on an armature 6 which are spaced upwardly from pairs of NC and NO contacts 3 and 4 mounted on a base 5 of the relay and are connected to the corresponding COM terminal lugs 4A mounted on the base 5 in spaced relation with respect to the sets of the NC and NO contacts 3 and 4. While on the other hand, in the card relay of lift-off type having a fixed or common (COM) contact between a pair of complementary movable contacts serving as NC and NO contacts, all these contact are normally mounted on a base of the relay so as to naturally result in the corresponding terminal arrangement of disposing the NC, COM and NO terminal lugs in this order. In fact, this NC-COM-NO relation corresponding to the arranging order of the contacts is the simplest for mounting on the base the several contacts together with the several terminal lugs. But, this NC-COM-NO terminal arrangement will render such card relays not to be compatible with the above relays of flexure type having NC-NO-COM terminal arrangement in the sense of using common wiring operations or common sockets. Accordingly, the card relays of lift-off type are mostly desired to have the same terminal arrangement as the relays of flexure type for increased versatility.